Add image extraction functionality with background removal

- Implemented ExtractImageRegion operator for extracting image regions using box or lasso selection.
- Added RemoveImageRegionBackground job for background removal from selected image regions.
- Created utility functions for polygon bounds, selection canvas creation, and applying selection masks.
- Integrated image processing using PIL and numpy for efficient pixel manipulation.
- Enhanced user experience with modal drawing and status updates during extraction.

mkdocs.yml

@@ -15,6 +15,7 @@ nav:
       - 粘贴剪贴板图片: clipboard-image.md
   - 使用指南:
       - 选择转换方式: workflows.md
+      - Image Box、Lasso 与 Perspective: image-tools.md
       - Mesh Plane: mesh-plane.md
       - Depth Plane: guide-depth-plane.md
       - Surface: guide-surface.md
@@ -24,6 +25,7 @@ nav:
       - 常见问题: faq.md
   - 参考与开发:
       - 功能参考: features.md
+      - Image 工具技术实现: image-tools-technical.md
       - Depth Plane 实现: depth-plane.md
       - Surface 实现: surface.md
       - 输出格式: outputs.md
@@ -83,6 +85,10 @@ markdown_extensions:
   - md_in_html
   - admonition
   - pymdownx.details
-  - pymdownx.superfences
+  - pymdownx.superfences:
+      custom_fences:
+        - name: mermaid
+          class: mermaid
+          format: !!python/name:pymdownx.superfences.fence_code_format
   - pymdownx.tabbed:
       alternate_style: true